Adjustable live-center unit



n w. r R o 2 3 9 m k W l 2 m 0 M n I47 V 1/ m i Q L Sept. 6, 1960 T. oLsoN ADJUSTABLE LIVE-CENTER UNIT Filed Dec. 17, 1956 United States Patent U ADJUSTABLE LIVE-CENTER UNIT Lester T. Olson, P.O. Box 551, Galt, Calif.

Filed Dec. 17, 1956, Ser. No. 628,734 2 Claims. c1. s2- -33 This invention relates in general to machine tools, and in particular to an improved live-center unit for use on the tailstock of a lathe, or in a similar adaptation.

The major object of this invention is to provide a unitas above-in which the live center is adjustable between a true or dead-center position for straight-cut work, and a selected radially offset position for taper-cut work.

Another important object of the invention is to provide the unit with a novel mechanism for adjusting the live center between the positions contemplated in the preceding paragraph; such mechanism being adapted for adjustment without the necessity of removing the livecenter unit from the tailstock of the lathe.

An additional object of the invention is to provide a live-center unit-for the purpose describedwherein the adjustment is accomplished by rotation of an inner cylindrical case nested in an outer cylindrical case; said cases being eccentric to the axis of the unit, and the inner case carrying the live center in journaled relation.

A further object of the invention is to provide a live center unit which is quite accurate in use, in that it cannot vary from any adjusted position. 7

It is also an object of the invention to provide a livecenter unit which is simple in structure and capable of ready and economical manufacture.

Still another object of the invention is to provide a practical, reliable, and durable adjustable live-center unit, and one which will be exceedingly effective for the purpose for which it is designed.

These objects are accomplished by means of such structure and relative arrangement of parts as will fully appear by a perusal of the following specification and claims.

In the drawings:

Fig. 1 is a side elevation, mainly in section, of the adjustable live-center unit.

Fig. 2 is a cross section taken on line 22 of Fig. 1.

Fig. 3 is a cross section taken on line 33 of Fig. 1.

Referring now more particularly to the drawings, and to the characters of reference marked thereon, the novel, adjustable live-center unit comprises a taper shank 1 adapted for reception in the tailstock of a lathe; such shank 1 merging at the front end in integral relation with a forwardly opening or cup-like, cylindrical outer case, indicated generally at 2. The outer case 2 is internally eccentric relative to the axis or center line of the unit (see Fig. 2).

A forwardly opening, cylindrical inner case, indicated at 3, is disposed 'in the outer case 2 and is rotatable or turnable therein with a relatively close fit. The inner case 3 is externally eccentric relative to the axis or center line of the unit; the eccentricity of the cases 2 and 3 being directly opposed when the unit is in a true or deadcenter position (see again Fig. 2).

The inner case 3 includes a rearwardly projecting, reduced-diameter neck 4 which turns in a reduced-diameter bore 2:: in the outer case 2; and said inner case 3 is retained in the outer case 2 by means of a front ring plate 5 secured in place by a snap ring 6.

2,951,407 Patented Sept. 6,1960

A rotary or live center 7 projects-in clearance relation-outwardly through, and to a termination a substantial distance beyond, the front ring plate 5; said live center 7 having a rearwardly projecting stub shank 8 carried in a combination thrust and anti-friction bearing 9. Such bearing 9 includes an inner race 10 engaged on the stub shank 8, and an outer race 11 fitted in the inner case 3 toward the front of the latter.

At its rear end the stub shank 8 of the live center 7 is formed with a reduced-diameter journal 12 carried in an anti-friction bearing 13 mounted in a cylindrical cage 14 having a closed rear end 15. v

At the front the cylindrical cage 14 is formed with a radial flange 16 which merges with a forwardly projecting annular foot 17; the latter bearing against the rear end of the outer race 11 of bearing 9.

The taper shank 1 is formed-throughout its length with a bore 18 in which an adjustment rod 19 is .slidably disposed. At its forward end the rod-19 bears against the closed rear end '15 of the cylindrical cage 14, while at its rear end said rod is abutted by an adjustment screw 29 threaded into the extreme rear end portion of said bore 18.

By adjusting the screw 20 the rod 19 is advanced; which in turn imparts forward motion to the cage 14, whereby the annular foot 17 urges the outer race 11 likewise forwardly, in order to adjust the combination thrustand anti-friction bearing 9.

As previously indicated, the rotary or live center 7 is in a true or dead-center position for straight-cut work when the outer case 2 and the inner case 3 have their eccentricity directly opposed.

In order to radially offset the live center 7for tapercut work-the inner case 3 is part-turned in the outer case 2; this being accomplished by the following adjusting mechanism:

The rearwardly projecting, reduced-diameter neck 4 of the inner case 3 is formed with a threaded peripheral groove 21 in which a tangential adjustment screw '22 seats with threading engagement; such adjustment screw 22 being carried, and turnable, in a bore 23 in the outer case 2.

While the screw 22 is turnable in the bore 23 it cannot move axially; this for the reason that said screw abuts a shoulder 24 at one end and is retained at the other end by a lock screw 25 threaded into said bore 23. At the end adjacent the shoulder 24 the screw 22 is formed with a transverse slot 26 for screw-driver reception, and by means of which said screw 22 can be manually turned in one direction or the other.

By such turning of the adjustment screw 22 the inner case 3 is caused to turn Within the outer case 2, and by reason of the eccentric relation of said cases the live center 7 is caused to move to a radially offset position for taper-cut work.

By reason of the use of adjusting mechanism as above described, the live center 7 cannot accidentally move or shift from any selected position, whether it be the true or dead-center position or a radially offset position.

In order that the operator may visually ascertain the adjusted position of the live center 7, the inner case 3 is formed exteriorly with a circurnferentially extending scale 27 readable through a slot 28 in the outer case 2; a pointer 29 registering with the scale 27 for accuracy in adjustment.

While the present invention preferably contemplates 3 stanti'ally fulfill the objects of the invention, as set forth herein.

While this specification sets forth in detail the present and preferred construction of the device, still in practice such deviations from such detail may be resorted to as do not form a departure from the spirit of the invention, as defined by the appended claims.

Having thus described the invention, the following is claimed as new and useful, and upon which Letters Patent are desired:

1. A center unit comprising an outer cylindrical case, a shank projecting axially from one end of the outer case, an inner cylindrical case mounted in the outer case for turning about an axis eccentric to said shank, a center secured in the inner case and projecting outwardly therefrom in a direction opposite the shank, and means normally but adjustably preventing turning of the inner case in the outer case; said means including, with an initially open-ended bore provided through the outer case tangential to and intersecting the periphery of the inner case, an adjustment screw disposed entirely within the bore and turnable therein, the inner case having a circumferential groove in which the screw threadingly engages, the bore having a reduced-diameter portion at one end forming an internal shoulder against which one end of the screw bears, said one end of the screw being recessed to receive a turning tool, and a retaining plug threaded into the other end of the bore to engage the adjacent end of the adjustment screw whereby, with the shoulder, to prevent axial movement of said screw.

2. A center unit comprising an outer stationary cylindrical case having a shank projecting axially from one end thereof and provided with a circular bore eccentric to the axis of the case and shank whereby the outer case is relatively thin for a certain portion of its circumference, an inner case turnably mounted in said bore, a center point mounted in the inner case, the outer case having a slot in said thin portion thereof and the inner case on its outer periphery being circumferentially scalemarked in position to be exposed in the slot, and means to rotatably adjust the inner case relative to the outer case and including an element mounted on the outer case and engaging the inner case within said outer case; said element being operable from a point on the outer case relatively close, to said slot, circumferentially of the case; the edge of the slot opposite the scale being formed with a pointer for cooperation with the scale markings.

References Cited in the file of this patent UNITED STATES PATENTS 1,051,531 Whipple Jan. 28, 1913 1,993,809 Schnelle Mar. 12, 1935 2,056,586 Rohm Oct. 6, 1936 2,103,912 Montgomery Dec. 28, 1937 2,374,325 Borek Apr. 24, 1945 2,499,131 Coles Feb. 28, 1950 2,549,613 Lee Apr. 17, 1951 2,709,924 Castelli June 7, 1955 2,711,935 Miles June 28, 1955 2,714,537 Studer Aug. 2, 1955 2,793,041 Barbier May 21, 1957 FOREIGN PATENTS 915,404 Germany July 22, 1954 B22784 Ib/49a Germany Aug. 30, 1956 1,052,332 France Sept. 23, 1953 

